We combined stage 1, 2 and 3 data using both meta-analysis approaches (fixed-effects model to combine ORs and weighted p value-based z-statistic combination across all sample sets) described above (Stage 1 meta-analysis). We also assessed our results using random effects meta-analysis (Supplementary Table 6). We observed some evidence for heterogeneity across studies (the I2 statistic ranged from 0 to 57.8% depending on SNP), with rs7578597 and rs10923931 displaying the largest fold differences in association p value between the fixed- and random-effects model analyses. Differences in strength of association across studies (leading to evidence for heterogeneity) could reflect interesting biological associations that vary from study to study depending on subject ascertainment scheme.
